Sunrise, “that” needs not to exist necessarily to make the segment complete. It is gramatically correct to leave the complementizer empty by virtue of the completeness of both the subject term and the predicate term. This erases enough ambiguity to reasonably distinguish the flow of the discourse.

Yeah, I had guessed that Oprah. And it is not gramatically correct because “your fraternity ‘isn’t doing it right’ ” cannot serve as the object of affirmation, while the addition of that encases it in a subordinate clause which can serve as a direct object.

I agree that it is a subordinate clause due to the nature of the ending being dependent on the initial element of the sentence. However, this specific instance yielded a circumstance of a special type of subordinate clause, the aforementioned “complementizer” which honors the ability to omit the “that” rendering it inessential. The complexity of the English language permits the possibility of correctness in meaning of multiple sentences written at variance.